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PubMed2000

PTW-diamond detector: dose rate and particle type dependence.

In this paper the suitability of a PTW natural diamond detector (DD) for relative and reference dosimetry of photon and electron beams, with dose per pulse between 0.068 mGy and 0.472 mGy, was studied and the results were compared with those obtained by a stereotactic silicon detector (SFD). The results show that, in the range of the examined dose per pulse the DD sensitivity changes up to 1.8% while the SFD sensitivity changes up to 4.5%. The fitting parameter, delta, used to correct the dose per pulse dependence of solid state detectors, was delta = 0.993 +/- 0.002 and delta = 1.025 +/- 0.002 for the diamond detector and for the silicon diode, respectively. The delta values were found to be independent of particle type of two conventional beams (a 10 MV x-ray beam and a 21 MeV electron beam). So if delta is determined for a radiotherapy beam, it can be used to correct relative dosimetry for other conventional radiotherapy beams. Moreover the diamond detector shows a calibration factor which is independent of beam quality and particle type, so an empirical dosimetric formalism is proposed here to obtain the reference dosimetry. This formalism is based on a dose-to-water calibration factor and on an empirical coefficient, that takes into account the reading dependence on the dose per pulse.

Diamond↗
PubMed1999

Dissociation of CH4 at high pressures and temperatures: diamond formation in giant planet interiors?

Experiments using laser-heated diamond anvil cells show that methane (CH4) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin. Infrared absorption and Raman spectroscopy, along with x-ray diffraction, indicate the presence of polymeric hydrocarbons in addition to the diamond, which is in agreement with theoretical predictions. Dissociation of CH4 at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH4, water, and ammonia, such as Uranus and Neptune.

Diamond↗
PubMed2001

endo-Fullerene and doped diamond nanocrystallite-based models of qubits for solid-state quantum computers.

Models of encapsulated nuclear spin 1/2 1H and 31P atoms in fullerene and diamond nanocrystallite, respectively, are proposed and examined with an ab initio local density functional method for possible applications as single quantum bits (qubits) in solid-state quantum computers. A 1H atom encapsulated in a fully deuterated fullerene, C20D20, forms the first model system and ab initio calculation shows that the 1H atom is stable in its atomic state at the center of the fullerene with a barrier of about 1 eV to escape. A 31P atom positioned at the center of a diamond nanocrystallite is the second model system, and 31P atom is found to be stable at the substitutional site relative to interstitial sites by 15 eV. Vacancy formation energy is 6 eV in diamond, so the substitutional 31P atom will be stable against diffusion during the formation mechanisms within the nanocrystallite. The coupling between the nuclear spin and the weakly bound (valance) donor electron in both systems is found to be suitable for single qubit applications, whereas the spatial distributions of (valance) donor electron wave functions are found to be preferentially spread along certain lattice directions, facilitating two or more qubit applications. The feasibility of the fabrication pathways for both model solid-state qubit systems within practical quantum computers is discussed within the context of our proposed solid-state qubits.

Computer Simulation↗
PubMed2003

A child with Diamond-Blackfan anemia, methylenetetrahydrofolate reductase mutation, and perinatal stroke.

Diamond-Blackfan anemia is a congenital hypoproliferative anemia known to be associated with diverse physical anomalies affecting the thumb, craniofacial bones, urogenital system, and heart; prematurity; and fetal demise. We report the case of a 16-month-old boy with Diamond-Blackfan anemia noted to have decreased use of his right side since birth. Magnetic resonance imaging demonstrated a large area of encephalomalacia in the left middle cerebral artery territory. Magnetic resonance angiography showed marked attenuation of the left middle cerebral artery, suggesting a remote thromboembolic event. The laboratory results were remarkable for a decreased hemogolobin of 9.5 g/dL and increased platelets of 591,000/microL. He was heterozygous for the methylenetetrahydrofolate reductase gene C677T mutation. An echocardiogram demonstrated a patent foramen ovale versus an atrial septal defect with left to right shunting. Perinatal stroke may be a rare complication of Diamond-Blackfan anemia in the setting of other risk factors.

Anemia, Diamond-Blackfan↗
PubMed1996

Assessing the cutting efficiency of dental diamond burs.

This study measured the cutting efficiencies of 15 types of roundend tapered conventional and disposable diamond burs. The results showed that disposable diamond burs had cutting efficiencies that were comparable to those of conventional (multiuse) diamond burs; their use should reduce the risk of clinical cross-infection.

Ceramics↗
PubMed2003

Using chemomechanically assisted diamond bur cutting for improved efficiency.

BACKGROUND: Surface active agents added to handpiece coolants enhance bur cutting rates, or CRs, through chemomechanical effects, or CMEs. The authors evaluate the effect of CMEs on long-term cutting by diamond burs. METHODS: The authors tested medium-grit diamonds in a high-speed handpiece under a 147.5-gram load at 350,000 revolutions per minute, with 22 milliliters per minute coolant flow consisting of distilled water or a 1:10 mouthwash/water mixture. Repeated 6-millimeter-long edge cuts were made through machinable glass ceramic bars until the CR (determined as the time to transect the bars) had decreased by more than 75 percent. The authors used six burs for each coolant and analyzed the data via one-way analysis of variance with post hoc Scheffé tests. RESULTS: CRs with water irrigation continuously decreased with the number of cuts and declined by 87 percent over eight cuts. The authors found faster CRs with CMEs; after 12 cuts, the CR was still close to 40 percent of the initial CR, compared with only 13 percent of the initial CR for water irrigation after eight cuts. These differences between CME-enhanced CRs and those found with water irrigation were statistically significant. CONCLUSIONS: Diluted alcohol- and glycerol-based mouthwash/water mixtures significantly enhanced the CRs of diamond burs and prolonged their service life by more than 50 percent compared with water irrigation alone. CLINICAL IMPLICATIONS: Dentists can increase bur CRs and extend bur cutting life by as much as 200 percent through the addition of diluted alcohol and glycerol mouthwash to the handpiece coolant.

Ceramics↗
PubMed2005

The effect of multiple uses of disposable diamond burs on restoration leakage.

BACKGROUND: The authors tested the clinical longevity of disposable diamond burs. They cut a series of five preparations and assessed the leakage after restoring the tooth. METHODS: The authors prepared 10 teeth for Class V restorations, and used a new disposable diamond bur for each tooth. The burs were used to cut preparations in extra teeth before being used to prepare a second series of 10 teeth (third use). The authors then cut preparations in extra teeth before preparing a third set of 10 teeth (fifth use). They removed existing restorations in a second group of 30 teeth and extended the preparations using the same regimen of one, three and five bur uses. All preparations were etched and conditioned, and the teeth were restored with resin-based composite. Using a 20-volt direct-current power source and a stainless-steel counter electrode, the authors measured the leakage electrochemically in 1.0 percent sodium chloride for 30 days. RESULTS: Freshly prepared and restored teeth leaked less than reprepared teeth. Leakage was similar for the first and third uses of the bur, but was far greater for the fifth use (P < .01). The previously restored teeth that were cut with the first- and third-use burs behaved the same, but the third-use bur caused more leakage than the fifth-use bur (P < .01). CONCLUSIONS: Reuse of disposable burs can affect leakage behavior. With new preparations, use of a disposable bur to cut more than three preparations increased leakage. For teeth that were reprepared and restored, greater leakage occurred than it did with new preparations, although repeated use of a bur may reduce leakage. CLINICAL IMPLICATIONS: Disposable diamond burs may cut preparations in up to three teeth before adversely affecting leakage behavior. Restoration removal and repreparation of teeth results in greater leakage than that with freshly prepared teeth.

Dental Cavity Preparation↗
PubMed2004

Wastewater treatment polymers identified as the toxic component of a diamond mine effluent.

The Ekati Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (< or =0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE.

Acrylic Resins↗
PubMed1996

Root surface removal with diamond-coated ultrasonic instruments: an in vitro and SEM study.

Adequate root preparation in periodontal procedures includes the removal of plaque, calculus, and perhaps contaminated cementum and dentin. The purpose of this study was to evaluate and compare the amount of root surface removal and residual surface texture using similarly shaped regular (US) and both fine (FINDIAM) and medium (MEDDIAM) grit diamond-coated ultrasonic inserts. Forty-five (45) premolars extracted for orthodontic reasons were randomly divided into 3 groups of 15 teeth each. They were individually mounted in a jig and instrumented with a standardized 500 gram force while they were moved a precise horizontal distance of 12 mm over a 1.2 second period using specially designed and computer controlled instrumentation. Three measurements were made to the nearest 0.0005" at 3 points along the test area before instrumentation and after 10 and 20 strokes. The mean depth of root structure removed was US 5.8 +/- 6.6 microns, FINDIAM 50.1 +/- 14.2 microns, MEDDIAM 30.8 +/- 12.1 microns, after 10 strokes, and US 12.7 +/- 10.9 microns, FINDIAM 83.3 +/- 20.1 microns, MEDDIAM 58.7 +/- 17.9 microns after 20 strokes, respectively. All 3 instruments were different from each other (P < 0.001) in the 10 stroke group, while in the 20 stroke group FINDIAM and MEDDIAM were different from US (P < 0.001), but not from each other. Only FINDIAM showed a significant difference between 10 and 20 stroke values for depth of root removal. Modified loss of tooth substance index SEM scores indicated increasingly greater root surface roughness from US to FINDIAM to MEDDIAM. Substantially greater root surface removal and greater residual root surface roughness occurred with diamond-coated ultrasonic inserts under standardized in vitro conditions. These results suggest that caution should be used with diamond-coated ultrasonic instruments during periodontal root planing procedures.

Analysis of Variance↗
PubMed1997

Clinical evaluation of the speed and effectiveness of subgingival calculus removal on single-rooted teeth with diamond-coated ultrasonic tips.

Several studies have found incomplete calculus removal during periodontal treatment with traditional hand curets, sonic, and ultrasonic instruments. This study evaluated the speed and effectiveness of subgingival calculus removal with new diamond-coated ultrasonic tips on single-rooted teeth. Single session subgingival scaling and root planing was performed on 80 teeth with 5 to 12 mm probing depths in 15 patients. Each patient provided groups of 4 teeth that were randomly treated with either hand curets (HAND); standard smooth ultrasonic tip (US); or fine grit (FINDIAM) or medium grit (MEDDIAM) diamond-coated ultrasonic tips. The time taken to reach the therapeutic endpoint of a clean, smooth root surface in a defined region on each tooth with each instrument by the 3 therapists with differing experience levels was recorded. The teeth were then atraumatically extracted, stored in a surfactant, photographed at 10X, and the percent of calculus present in the area of the pocket or on a comparable control surface calculated by histometric point counting. ANOVA and paired t tests showed that mean percent remaining calculus on treated versus control surfaces was HAND 4.6 +/- 5.3 versus 57.5 +/- 28.2, US 4.7 +/- 6.4 versus 54.4 +/- 25.9, FINDIAM 4.3 +/- 5.2 versus 37.5 +/- 22.1, and MEDDIAM 3.4 +/- 4.2 versus 50.7 +/- 20.1, respectively (all P < 0.01). The mean time in seconds to reach the clinical endpoint ranged from HAND 289 +/- 193, US 194 +/- 67, FINDIAM 167 +/- 71, to MEDDIAM 147 +/- 92. All powered instruments were significantly faster than HAND (P < 0.05), but did not differ from each other. On a 0 = "smooth" to 3 = "rough" scale, most often HAND resulted in "smooth" surfaces (10/20), the powered tips of all types "slight" surface roughness (10/20 each), and US the most "moderate" roughness (7/20). There were no differences in percent calculus remaining, surface roughness, or time spent among the 3 treating clinicians despite their varying experience levels. The results of this study showed that percent calculus remaining was <5% with all the instruments given time ad libitum on a given root surface. Root roughness was generally slightly greater with all 3 powered tips. All of the powered instruments took significantly less time than the HAND. Both DIAM tips took less time than US. Diamond-coated ultrasonic tips appeared to be much more efficient than HAND or US in removing calculus in moderate-deep probing depths on single-rooted teeth in vivo.

Adult↗
PubMed2000

In vitro study of enamel and dentin marginal integrity of composite and compomer restorations placed in primary teeth after diamond or Er:YAG laser cavity preparation.

PURPOSE: The aim of this in vitro study was to evaluate the effect of laser vs diamond instruments on Class II and Class V cavity margins in primary teeth with SEM after restoration with composite and compomer materials and subsequent thermocycling. MATERIALS AND METHODS: Class V cavities with margins completely located in enamel were prepared in 36 extracted primary teeth to examine the restoration-enamel interface. Eighteen cavities were prepared with an Er:YAG laser operated at 3 Hz, 300 mJ/pulse, and 18 with a spherical fine diamond bur. In 24 primary teeth, Class II cavities with cervical proximal margins located in dentin were prepared for examination of the restoration-dentin interface. All Class II cavities were prepared with a conventional cylindrical diamond bur. In 12 cavities, the margins located in dentin were conditioned with an Er:YAG laser (1 Hz, 100 mJ/pulse). All cavities were restored with a fine hybrid composite resin or a compomer material. RESULTS: SEM examination of Class V cavities after thermocycling (between 5 degrees C and 55 degrees C, 2500 cycles) revealed over 90% "perfect" margins in all composite fillings and in those compomer restorations applied after conventional preparation and acid etching. Compomer restorations placed without acid etching revealed a significantly superior marginal integrity in laser-prepared cavities (81% perfect margins) vs conventionally prepared cavities (60% perfect margins). SEM analysis of the dentinal margins of both compomer and composite restorations in Class II cavities showed mean percentages of perfect marginal adaptation ranging from only 13% to 66%. CONCLUSION: Er:YAG laser treatment can be recommended for composite restorations in Class V cavities in primary teeth. Compomer restorations can be placed after conventional preparation of Class V cavities and acid etching or after laser preparation. Dentin bonding in Class II cavities in primary teeth is not sufficient and cannot be improved with Er:YAG laser pretreatment.

Acid Etching, Dental↗
PubMedDate not supplied

[Dominant form of Diamond-Blackfan anemia].

Diamond-Blackfan anaemia (congenital hypoplastic anaemia) is a rare hereditary disease with isolated congenital hypoplasia of red blood cells precursors in bone marrow, and its important characteristic is successful treatment. Most of the patients become symptomatic in the first year of life and it lasts lifelong. In 25% of patients with Diamond-Blackfan anaemia 19q13 gene mutation was detected, and recent findings suggest another gene located on 8p23.3-p22 chromosome. Two sisters with mild clinical manifestations of Diamond-Blackfan anaemia were studied at the Department of Paediatrics in the Osijek University Hospital. First symptoms in both of these patients were noticed at the age of 5 months. Bone marrow puncture showed isolated hypoplasia of morphologically normal red blood cells precursors. Patients responded well to corticosteroid therapy. All members of patients' family were genetically tested for known loci for this disease, but tests showed no genetical abnormalities. Diagnosis was made by clinical symptoms, cytological findings and ex iuvantibus. We believe that patients are in the group with good outlook, since minimal steroid therapy stabilized their symptoms, and they developed no addiction either to high-dosed steroids, or to transfusions.

Anemia, Diamond-Blackfan↗
PubMed2004

Effects of diamond bur particle size on dentin bond strength.

PURPOSE: To evaluate the influence of particle size of originally designed diamond burs on resin adhesion to sound young human permanent dentin. METHODS: The buccal surfaces of 105 premolars were used. Six test groups were prepared. The adhesive systems and resin-based composites used for Groups 1-3 were Clearfil SE Bond (SE) and Clearfil AP-X, and for Groups 4-6, Single Bond (SB) and Z250. Flat dentin surfaces were finely ground with 25 microm particle size IW-G5 diamond bur (IW-G5, Groups 1 and 4), 50 microm particle size IW-G4 diamond bur (IW-G4, Groups 2 and 5), or 600-grit SiC paper (#600, Groups 3 and 6). The microstructure of the prepared dentin, SE primed or SB etched dentin, and resin-dentin interfaces of each group (3 teeth/group) were studied using SEM. Shear bond strengths (SBS) in MPa were tested (10 teeth/group), and the failed surfaces were observed using SEM. Data was statistically analyzed using ANOVA and Fisher's PLSD at P < 0.05. RESULTS: The dentin ground with the IW-G5 or IW-G4 bur was rougher than the dentin ground with the 600-grit SiC paper. The mean SBS (MPa) for Groups 1-6 were: 32.3 +/- 5.0, 27.6 +/- 6.4, 21.3 +/- 3.6, 5.9 +/- 2.9, 6.5 +/- 3.1 and 5.3 +/- 2.0. The SBS of Groups 1-3 (SE groups) were significantly higher than those of Groups 4-6 (SB groups). The SBS of Group 1 (IW-G5, SE group) was significantly higher than those of Groups 2 (IW-G4, SE group) and 3 (#600, SE group), and the SBS of Group 2 was significantly higher than that of Group 3. There was no significant difference for SBS among Groups 4, 5 and 6. Fracture mode after SBS test mainly showed mixed fracture (adhesive and cohesive resin fracture) for the SE groups, and adhesive fracture for the SB groups.

Analysis of Variance↗
PubMed2004

[Electrocatalytic behavior of diamond electrode for organic pollutant].

The physical and electrochemical behaviors of the boron-doped diamond film electrode prepared by chemical vapor deposition technique were studied. The surface microstructure of the electrode was demonstrated by means of scanning electron microscopy. The electrochemical behaviors of the electrode were investigated using cyclic voltammetry and AC Impedance. The diamond films were polycrystalline and had uniform grains in micron grade. The results showed that the electrode had a very wide potential window and very low background current. The potential windows in acidic, neutral or alkaline medium were separately 4.3 V, 4.0 V and 3.0 V. The background current was as low as -9 x 10(-6)-5 x 10(-7) A. In electrolyte including Ferri/Ferrocyanide, the electrode surface kept good activity, and the electrochemical reaction carrying out on the surface was a diffusion-controlled reaction, with good quasi-reversibility. Studies of the oxidation of organic compounds showed that the electrocatalytic oxidation behavior was selective. Compared with Pt and graphite electrodes, the diamond electrode could oxidate aromatic compounds like phenol and nitrobenzene effectively, and the process of oxidation was very simple and complete.

Catalysis↗
PubMed2005

[Cytoarchitecture of lymphoid tissue in tracheal mucosa as affected by diamond dust].

The effect of diamond dust on lymphoid aggregates in tracheal mucosa after the exposure for various time periods was studied in mature Wistar rats, which were placed under the natural conditions of diamond-processing factory. Exposure to diamond dust resulted in the changes of cell content of lymphoid aggregates in tracheal mucosa already at the early stages of an experiment (Day 3). The proportion of small lymphocytes was decreased, while the content of medium lymphocytes and undifferentiated cells was increased simultaneously with the augmentation of the number of macrophages and cells undergoing destruction. At Day 30 in subepithelial area and in the basal region of lymphoid nodules, the reduction of the number of small lymphocytes was also accompanied by the significant increase of macrophages and cells undergoing destruction.

Animals↗
PubMedDate not supplied

Comparing cutting efficiencies of diamond burs using a high-speed electric handpiece.

This study sought to compare the cutting efficiency of different diamond burs on initial use as well as during repeated use, alternating with sterilization. Long, round-end, tapered diamond burs with similar diameter, profile, and diamond coarseness (125-150 microm grit) were used. A high-torque, high-speed electric handpiece (set at 200,000 rpm) was utilized with a coolant flow rate of 25 mL/min. Burs were tested under a constant load of 170 g while cuts were made on a machinable ceramic substrate block. Each bur was subjected to five consecutive cuts for 30 seconds of continuous operation and the cutting depths were measured. All burs performed similarly on the first cut. Cutting efficiencies for three of the bur groups decreased significantly after the first cycle; however, by the fifth cycle, all bur groups performed similarly without any significant differences (p > 0.05). A scanning electron microscope revealed significant crystal loss after each use.

Ceramics↗
PubMedDate not supplied

[Study on the causes for some characteristic damages of diamond instruments for dental practice].

An attempt has been made for investigation and classification of the causes for diamond instruments for dental practice resource decrease. The overheating of the instruments is considered to be the main cause and the plastic materials smudges and unstable fixing of the diamond grains--as accompanying causes. Taking in consideration the above mentioned factors could contribute to a more rational use of the diamond instruments for dental practice.

Carbon↗
PubMed1999

Exclusion of linkage of Shwachman-Diamond syndrome to chromosome regions 6q and 12q implicated by a de novo translocation.

Shwachman-Diamond syndrome is a rare genetic disorder of unknown pathogenesis involving exocrine pancreatic insufficiency and hematological and skeletal abnormalities. There is broad clinical variability; the extent of heterogeneity is unknown but comparisons within a large cohort of patients show no striking differences between patients of families with single or multiple affected offspring. Segregation analysis of a cohort of 69 families has suggested an autosomal recessive mode of inheritance. A single constitutional de novo chromosome rearrangement was reported in a Japanese patient involving a balanced translocation, t(6;12)(q16.2;q21.2), thereby suggesting possible loci for a genetic defect. Evenly spaced microsatellite markers spanning 26-32 cM intervals from D6S1056 to D6S304 and D12S375 to D12S346 were analyzed for linkage in members of 13 Shwachman-Diamond syndrome families with two or three affected children. Two-point lod scores were calculated for each marker under assumptions of recessive inheritance and complete penetrance. Negative lod scores indicated exclusion of both chromosome regions. Further, affected sibs were discordant for inheritance of chromosomes in most families based on constructed haplotypes. The cytogenetic abnormality is not associated with most cases of Shwachman-Diamond syndrome.

Bone and Bones↗